1. Field of the Invention
The present invention relates to a radiological image detection device which detects a radiological image.
2. Description of the Related Art
In recent years, in a medical field, in order to perform an image diagnosis, a radiological image detection device has been used in which radiation (for example, X-rays), which is emitted toward a radiographed part of a patient from a radiation source and is transmitted through the radiographed part, is detected and is converted into electric charge, and image data indicating a radiological image of the radiographed part is generated based on this electric charge. As the radiological image detection device, there are a direct conversion type device which directly converts radiation into electric charge and an indirect conversion type device which temporarily converts radiation into visible light and converts the visible light into electric charge.
The indirect conversion type radiological image detection device includes a scintillator (phosphor layer) which converts radiation into visible light and a photoelectric conversion panel which detects and converts the visible light into electric charge. Cesium iodide (CsI) or gadolinium oxide sulfur (GOS) is used in the scintillator.
CsI has higher manufacturing costs than GOS, but has high conversion efficiency when turning radiation to visible light. CsI also has a columnar crystal structure, has an improved SN ratio of image data due to a light guide effect, and is, thus, used as, a scintillator of a high-end oriented radiological image detection device in particular. However, emission efficiency is low when only CsI is used, and thus an augmenting agent such as thallium (Tl) or sodium (Na) is added to CsI. The columnar crystal structure is a structure in which a plurality of columnar crystals soar on a substrate and air is interposed between the adjacent columnar crystals.
A scintillator with the columnar crystal structure such as CsI has a problem of being deliquescent. For this reason, the scintillator with the columnar crystal structure is covered with a moisture-proof surface protection film such as poly-para-xylyene so as to prevent deliquescence (for example, refer to JP2008-8741A).
In JP2008-8741A, the scintillator with the columnar crystal structure is formed on a substrate through deposition, the substrate and the scintillator are covered with a surface protection film, and front end sides of columnar crystals of the scintillator are opposite a photoelectric conversion panel. In addition, in a radiological image detection device disclosed in JP2008-8741A, the surface protection film partially penetrates between the adjacent columnar crystals on the front end side of the columnar crystal.
JP2008-8741A discloses that, since the refractive index of the surface protection film is closer to the refractive index of the columnar crystal than that of air, the surface protection film is interposed between (gap) the adjacent columnar crystals, thus light is likely to be leaked from columnar crystals to the gap, and thereby a light guide effect is reduced.